WDPN31 PGTW 031500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (MAN-YI) WARNING 
NR 08// 
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 031200Z6 TO 061200Z9 AUG 01.
   A. TYPHOON (TY) 12W (MAN-YI) LOCATED APPROXIMATELY 140 NM NORTH-
NORTHEAST OF SAIPAN, HAS TRACKED NORTHWESTWARD AT 16 KNOTS DURING 
THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 031130Z8 
INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON 
CURRENT SATELLITE INTENSITY ESTIMATES OF 77 KNOTS. ANIMATED ENHANCED 
INFRARED SATELLITE IMAGERY DEPICTS AN INCREASE IN CONVECTION OVER 
THE PAST 12 HOURS AS THE SYSTEM CONTINUES TO ORGANIZE. 
   B. TY 12W IS CURRENTLY UNDER THE STEERING INFLUENCE OF THE LOW TO 
MID LEVEL SUBTROPICAL RIDGE TO THE NORTHEAST. THE NOGAPS (NGPS), 
GEOPHYSICAL FLUID DYNAMIC NAVY (GFDN), UK-MET OFFICE (EGRR), 
JAPANESE GLOBAL SPECTRAL (JGSM) AND THE JAPANESE TYPHOON (JTYM) 
MODELS ARE IN VERY GOOD AGREEMENT AS THEY TRACK THE SYSTEM 
NORTHWESTWARD THROUGH THE 36 HOUR PERIOD. AFTER THIS TIME, THE 
MODELS TRACK THE SYSTEM SLOWLY NORTHWARD AND NORTH-NORTHEASTWARD 
INTO A WEAKNESS IN THE RIDGE THROUGH THE 72-HOUR PERIOD. THE 
NUMERICAL CONSENSUS (NCON) CONSISTS OF FIVE MODELS: NGPS, GFDN, 
EGRR, JGSM, AND JTYM. THE OFFICIAL FORECAST IS A BLEND OF 
PERSISTENCE AND NCON THROUGH 24 HOURS WITH THE REMAINING FORECAST 
POSITIONS BASED ON NCON.
   C. TY 12W IS FORECAST TO INTENSIFY THROUGH THE 48 HOUR FORECAST 
PERIOD AS IT MOVES OVER INCREASING SEA SURFACE TEMPERATURES (SST) 
AND UNDER AN IMPROVING UPPER-LEVEL ENVIRONMENT. THE SYSTEM SHOULD 
BEGIN TO WEAKEN SLIGHTLY BY 72 HOURS AS IT MOVES OVER SLIGHTLY 
COOLER SST.
   D. WIND RADII ARE BASED ON A 030823Z6 QUIKSCAT PASS AND 
CLIMATOLOGY FOR AN AVERAGE SIZE SYSTEM.
   E. THE JTWC WEBSITE HAS CHANGED TO: 
HTTPS://WWW.NPMOC.NAVY.MIL/JTWC.HTML. THIS CHANGE IS FOR SECURITY 
REASONS ONLY. THE CONTENT OF THE WEBSITE HAS NOT CHANGED.//
FORECAST TEAM: CANTRELL/VILPORS/BALDINGER/SHERRY//



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